Earth-boring tools are used to form boreholes (e.g., wellbores) in subterranean formations. Some earth-boring tools, such as roller cone drill bits and hybrid drill bits, include a rotational bearing between a non-rotating member and a rotating member such as a roller cone including cutting elements. A bearing seal may protect the bearing by inhibiting the ingress of drilling fluid and formation cuttings to the bearing and by at least partially preventing discharge of lubricant (e.g., grease) used to lubricate both the bearing and the seal. One type of seal used in such tools employs primary metal-to-metal face seals that are energized by, for example, an elastomeric ring. Such a seal may be referred to as a rigid face seal or a metal face seal. Such seals may include at least one rigid ring having a seal face thereon, and an energizing element, which urges the seal face of the rigid ring into sealing engagement with a second sealing face. One or both of the sealing faces may be coated with a wear-resistant coating, such as diamond-like carbon (DLC). Embodiments of such bearing seals are disclosed in U.S. Pat. No. 7,413,037 to Lin et al., issued Aug. 19, 2008, and assigned to the assignee of the present disclosure (the '037 patent), which is hereby incorporated by reference for all it contains.
As disclosed in the '037 patent, the rigid ring may be confined in a groove near the base of the shaft on which the roller cone is rotatably affixed. The second sealing face may be disposed on a sealing element (e.g., a steel ring) pressed into a cavity of the roller cone, and the energizing element may be located adjacent the base of the shaft and circumferentially inward from the rigid ring. Such an arrangement may require a certain minimum axial length of the bearing and seal assembly. Furthermore, relative rotational movement between the energizing element and one or both of the rigid ring and the shaft may occur in the event that the rigid ring sticks to the sealing element in the roller cone, resulting in poor sealing and rapid degradation of the energizing element. Finally, if an inward force is applied to the roller cone (i.e., a force urging the cone radially inward toward a rotational axis of a body of the bit) the biasing force provided by the energizing element may be reduced, compromising the seal and allowing lubricant to leak from the seal and/or allowing drilling fluid and formation cuttings to contaminate the bearing.